Russia's lower house of parliament has given final approval to a contentious bill that retaliates against a new US human rights measure by barring Americans from adopting the country's children.
Washington swiftly slammed the move saying Russian children would be harmed by the measure.
The State Duma passed the bill without debate in a quick 420-7 vote on Friday as protesters picketed the building demanding the measure be voted down.
But the vote took place in a largely ceremonial third and final reading of the legislation, and its outcome was never in doubt.
"We regret the results of today's Duma vote," US Ambassador Michal McFaul tweeted shortly after the decision.
He told the Interfax news agency separately that the United States was "extremely concerned" by the law's provisions.
The Kremlin-dominated upper house is now expected to approve the ban next Wednesday before passing it on to President Vladimir Putin for his signature.
The Russian leader has indicated he is ready to put his name on the measure so that it could enter law on January 1.
The measure, which underscores the severity of the recent strain in Russia-US ties, would end about 1,000 adoptions a year.
Caregivers in particular fear the new rules will hit the most disadvantaged children because foreign adoptive parents are often ready to adopt kids rejected by Russian families.
Acting US State Department spokesman Patrick Ventrell said the bill would ultimately have the effect of keeping Russian children from growing up in loving households in the United States.
"What this would do is prevent children from growing up in a family environment of happiness, love and understanding," he said.
"And so that's the basic premise of our bilateral adoption agreement. It's something we've worked for many months with the Russians on. And so really it's Russian children who would be harmed by this measure."
The affair has also highlighted cabinet splits between those who subscribe to strong anti-US rhetoric and those who prefer to cast Moscow as a more reasoned partner.
Several senior government figures at one stage accused deputies of playing a risky game of populist politics that risked further upsetting relations between Moscow and Washington.
Foreign Minister Sergei Lavrov flatly called the ban "a mistake," in a rare instance of a top diplomat disagreeing with what appeared to be the leadership's position on the most controversial domestic issue of the day.
Putin hesitated for nearly a week before backing the measure during his annual press conference on Thursday.
"I understand that this was an emotional response by the State Duma, but I think that it was appropriate," Putin told reporters.
Russia's legislative move comes after US President Barack Obama last week signed into law the Magnitsky Act -- a measure paying tribute to a Russian lawyer who died in custody in Moscow in 2009 after blowing the whistle on a $235 million police embezzlement scheme.
His family and his employer Hermitage Capital -- once Russia's largest Western investment fund -- both believe that he was tortured in prison and died as a result of his beatings.
Russian investigators have dismissed those charges and are still pursuing a fraud case against the late Magnitsky himself.
They have also refused to follow up allegations from Hermitage Capital that some of the most senior security officials -- including ministers -- were involved in the embezzlement scheme.
Russia has used adoption in the past to take out its frustration on some US policy decisions.
Moscow previously placed moratoriums on adoptions, and now issues formal foreign policy statements whenever adopted Russian children are harmed in the United States.
The numbers of children taken in by US families fell to 956 last year from 1,773 three years earlier.
"We had wonderful families from the United States. We have absolutely no complaints about them," said Natalia Karanevskaya, a paediatrician at a Moscow children's home.
"They took the most difficult children that would have never been taken in Russia," she told AFP.
"This law will have its effects."